The present invention relates to a printed circuit board and its manufacturing method. More particularly, the present invention relates to a so-called composite printed circuit board which comprises resin substrates laminated on a ceramic substrate and also relates to a manufacturing method of the composite printed circuit board.
A so-called composite printed circuit board, comprising resin substrates laminated on a ceramic substrate, is conventionally known as a printed circuit board which is capable of assuring excellent heat radiation and other thermal properties as well as realizing high-density electric component mounting.
The composite printed circuit board is manufactured in the following manner.
First, a uncured state heat-hardening resin (e.g., a polyimide resin or the like) is coated on a ceramic member (i.e., a ceramic substrate) on which a printed conductor pattern and a printed resistor are formed. Next, a laser beam is applied to a predetermined portion on a heat-hardening resin layer to open a via-hole so as to extend across this resin layer. Then, a conductor pattern and a via are formed on or in the heat-hardening resin layer by plating or sputtering.
When a plurality of resin substrates are laminated, another uncured state heat-hardening resin is coated on the hardened heat-hardening resin. Then, the above-described processes are repeated to obtain a composite printed circuit board having a desired number of resin layers.
However, the above-described conventional technique requires a large number of manufacturing processes starting from the step of coating the uncured state heat-hardening resin on the ceramic substrate to the step of forming the conductor pattern and the via. When the required number of layers constituting the composite printed circuit board is large, similar steps must be repeated to build up the layers. The manufacturing processes become very complicate.